Studies on inflammation in atherosclerosis
A spectrum of chronic inflammation is commonly seen in association with advanced human atherosclerosis. This local complication of advanced atherosclerosis is termed 'chronic periaortitis'. This may be seen sub-clinically in necropsy samples or may present clinically, in more severe cases, as the conditions previously termed 'idiopathic retroperitoneal fibrosis', 'inflammatory aneurysm' or 'peri-aneurysmal retroperitoneal fibrosis'. The inflammatory cells consist of lymphocytes and plasma cells. Thinning or breaching of the media is common to all forms. A histological survey of necropsy material and surgical material has confirmed the unifying concept of chronic periaortitis. Histochemical, immunohistochemical, immunofluorescence and electron microscopy have been used in this study to examine the nature of the inflammatory response. Locally activated B lymphocytes are stimulated to produce immunoglobulin, predominantly IgG, to oxidised low density lipoprotein (LDL) and ceroid elaborated with human atheroma. T helper lymphocytes and HLA-DR positive cells mediate this response. These findings have been confirmed using in vitro culture of lymphocytes derived from tissue and peripheral blood of patients with chronic periaortitis. Antibodies to oxidized LDL and ceroid have been detected in serum from patients with chronic periaortitis using a modified ELISA technique. This has led to the development of a potential diagnostic test for chronic periaortitis. These results support the hypothesis that chronic periaortitis has an auto-allergic cause and that the allergen is a component of ceroid, likely to be oxidized LDL, elaborated in human atherosclerotic plaques.